Method and apparatus for controlling an actuatable restraining device using switched thresholds based on transverse acceleration

ABSTRACT

The present invention is directed to controlling a vehicle multistage actuatable occupant restraining system ( 14, 18 ). A crash sensor ( 32, 36 ) senses crash acceleration and provides a crash acceleration signal ( 110, 160 ) indicative thereof. Crash velocity and crash displacement are determined ( 118, 168 ) in response to the crash acceleration signal. A first stage ( 90, 94 ) of the multistage actuatable occupant restraining system is actuated when the determined crash velocity as a function of crash displacement exceeds a low threshold ( 130, 132, 180, 182 ). A transverse accelerometer ( 34 ) senses transverse crash acceleration. The transverse acceleration as a function of the crash displacement is compared ( 226, 278 ) against a transverse threshold ( 268 ). The value of the low threshold ( 130, 180 ) is switched to a different value ( 132, 182 ) when the transverse acceleration exceeds the transverse threshold.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for controllinga vehicle actuatable occupant restraining device.

BACKGROUND OF THE INVENTION

Air bag restraining systems in vehicles for vehicle occupants are knownin the art. An air bag restraining device may include a multistageinflator where the stages are actuated at different times in response tovehicle crash conditions.

U.S. Pat. No. 5,935,182 to Foo et al., assigned to TRW Inc., discloses amethod and apparatus for discriminating a vehicle crash condition usingvirtual sensing. U.S. Pat. No. 6,036,225 to Foo et al., assigned to TRWInc., discloses a method and apparatus for controlling a multistageactuatable restraining system in a vehicle using crash severity indexvalues. U.S. Pat. No. 6,186,539 to Foo et al., also assigned to TRWInc., discloses a method and apparatus for controlling a multistageactuatable restraining device using crash severity indexing and crushzone sensors.

SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus forcontrolling a vehicle multistage actuatable occupant restraining system.A crash sensor senses crash acceleration and provides a crashacceleration signal indicative thereof. Crash velocity and crashdisplacement are determined in response to the crash accelerationsignal. A first stage of the multistage actuatable occupant restrainingsystem is actuated in response to the determined crash velocity as afunction of crash displacement exceeding a low threshold. A transverseaccelerometer senses transverse crash acceleration. The transverseacceleration as a function of the crash displacement is compared againsta transverse threshold. The value of the low threshold is switched to adifferent value when the transverse acceleration exceeds the transversethreshold.

In accordance with another embodiment, the present invention is directedto a method and apparatus for controlling a vehicle multistageactuatable occupant restraining system. A crash sensor senses crashacceleration and provides a crash acceleration signal indicativethereof. Crash velocity and crash displacement are determined inresponse to the crash acceleration signal. A first stage of themultistage actuatable occupant restraining system is actuated inresponse to the determined crash velocity as a function of crashdisplacement exceeding a low threshold. A transverse accelerometersenses transverse crash acceleration. The transverse acceleration as afunction of the crash displacement is compared against a transversethreshold. A crush zone accelerometer senses crush zone acceleration.The crush zone acceleration as a function of the crash displacement iscompared against a crush zone threshold. The value of the low thresholdis switched to a different value when at least one of the transverseacceleration exceeds the transverse threshold and the crush zoneacceleration exceeds the crush zone threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention willbecome apparent to one skilled in the art upon consideration of thefollowing description of the invention and the accompanying drawings inwhich:

FIG. 1 is a schematic diagram of a vehicle having an actuatable occupantrestraining system with a control arrangement in accordance with oneembodiment of the present invention;

FIG. 2 is a schematic block diagram of the actuatable occupantrestraining system shown in FIG. 1;

FIG. 3 is a functional block diagram of a portion of an actuatableoccupant restraining system of FIG. 2; and

FIG. 4 shows graphical representations of determined crash relatedvalues and thresholds used in the control arrangement of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, an actuatable occupant restraining system10, in accordance with the present invention, in a vehicle 12, includesa driver's side, multistage, front actuatable restraining device 14, anda passenger's side, multistage, front actuatable restraining device 18.Other actuatable restraining devices could be included such as adriver's actuatable side restraining device 16 and a passenger'sactuatable side restraining device 20. The actuatable occupantrestraining system 10 could further include a driver's side pretensioner22, and a passenger's side pretensioner 24. The present invention is notlimited to use with an air bag restraining system. The present inventionis applicable to any actuatable restraining device having multipleactuatable stages or to a plurality of actuatable restraining devicesthat can be simultaneously or sequentially actuated. A front air baghaving plural actuatable stages is described for purposes ofexplanation. The invention is also applicable to a vehicle havingmultiple air bags wherein at least one of the air bags is a multistageair bag controlled in accordance with the present invention.

The system 10 includes at least one crash or collision sensor assembly30 located at a substantially central location of the vehicle.Preferably, sensor assembly 30 includes a first crash accelerationsensor 32 having its axis of sensitivity substantially oriented to sensecrash acceleration in the vehicle X direction (i.e., parallel with thefront-to-rear axis of the vehicle) that provides a crash accelerationsignal designated CCU_1X. The sensor assembly 30 further includes asecond crash acceleration sensor 34 having its axis of sensitivitysubstantially oriented to sense crash acceleration in the vehicle Ydirection (i.e., perpendicular to the front-to-rear axis of the vehicle)that provides a transverse crash acceleration signal designated CCU_1Y.The sensor assembly 30 further includes a third crash accelerationsensor 36 having its axis of sensitivity substantially oriented to sensecrash acceleration in the vehicle X direction (i.e., parallel with thefront-to-rear axis of the vehicle) that provides a crash accelerationsignal designated CCU_2X.

The crash acceleration signals from the crash sensors 32, 34, 36 cantake any of several forms. Each of the crash acceleration signals canhave amplitude, frequency, pulse duration, etc., or any other electricalcharacteristics that vary as a function of the sensed crashacceleration. In accordance with a preferred embodiment, the crashacceleration signals have frequency and amplitude characteristicsindicative of the sensed crash acceleration.

In addition to the crash acceleration sensors 32, 34, 36, the systemincludes forwardly located crush zone sensors 40, 42 located in a crushzone location of the vehicle 12. The sensor 40 is located on thedriver's side of the vehicle and has its axis of sensitivitysubstantially oriented to sense crash acceleration parallel with thevehicle's X axis. The sensor 42 is located on the passenger's side ofthe vehicle and has its axis of sensitivity substantially oriented tosense crash acceleration parallel with the vehicle's X axis. The signalfrom the driver's side, crush zone sensor 40 is designated as CZS_3X andthe signal from the passenger's side, crush zone sensor 42 is designatedas CZS_4X.

The signals from the crush zone sensors 40, 42 also have frequency andamplitude characteristics indicative of the crash accelerationexperienced at those sensor locations of the vehicle. The crush zonesensors are preferably mounted at or near the radiator location of thevehicle and serve to better discriminate certain types of crashconditions by supplementing the indications provided by the crashsensors 32, 34, 36.

A driver's side crash acceleration sensor 46 is mounted on the driver'sside of the vehicle and has an axis of sensitivity substantiallyoriented to sense crash acceleration parallel with the vehicle's Y axis.The crash acceleration sensor 46 provides a crash acceleration signaldesignated as RAS_1Y having frequency and amplitude characteristicsindicative of crash acceleration in the Y axis direction withacceleration into the driver's side of the vehicle having a positivevalue. A passenger's side crash acceleration sensor 48 is mounted on thepassenger's side of the vehicle and oriented to sense crash accelerationparallel with the vehicle's Y axis. The crash acceleration sensor 48provides a crash acceleration signal designated as RAS_2Y havingfrequency and amplitude characteristics indicative of crash accelerationin the Y axis direction with acceleration into the passenger's side ofthe vehicle having a positive value.

The crash acceleration signals CCU_1X, CCU_1Y, CCU_2X, CZS_3X, CZS_4X,RAS_1Y, and RAS_2Y are provided to a controller 50, through associatedhardware high pass/low pass filters 52, 54, 56, 58, 60, 62, and 64,respectively. The controller 50 is preferably a microcomputer. Althoughthe preferred embodiment of the invention uses a microcomputer, theinvention is not limited to the use of a microcomputer. The presentinvention contemplates that the functions performed by the microcomputercould be carried out by other digital and/or analog circuitry and can beassembled on one or more circuit boards or as an application specificintegrated circuit (“ASIC”).

The filters 52-64 filter the crash acceleration signals to removefrequency components that are not useful in discriminating a vehiclecrash event, e.g., frequency components resulting from road noise.Frequencies useful for crash discrimination can be determined throughempirical testing of a vehicle platform of interest.

The controller 50 monitors the filtered crash acceleration signals andperforms one or more crash algorithms to discriminate whether a vehicledeployment or non-deployment crash event is occurring. Each crashalgorithm measures and/or determines values of the crash event from thecrash acceleration signals. These values are used in deployment andactuation decisions. Such measured and/or determined crash values arealso referred to as “crash metrics” and include crash acceleration,crash energy, crash velocity, crash displacement, crash jerk, etc. Basedupon the crash acceleration signals, the controller 50 furtherdetermines crash severity index values for a crash event using crashseverity metrics (described below) and uses these determined crashseverity index values in the control of the multistage actuatablerestraining devices 14, 18.

Other driver associated sensors are used to detect characteristics ofthe driver that are or could be used by the controller 50 in its controlalgorithm to control the actuatable restraining devices 14 and 16. Thesesensors include a driver's buckle switch sensor 70 that provides asignal to controller 50 indicating whether the driver has his seat beltbuckled. Driver's weight sensors 72 located in the driver's seat 74provide a signal indicative of the driver's sensed weight. Other driverassociated sensors 76 provide other driver related information to thecontroller 50 such as position, height, girth, movement, etc.

Other passenger associated sensors are used to detect characteristics ofthe passenger that are or could be used by the controller 50 in itscontrol algorithm to control the actuatable restraining devices 18 and20. These sensors include a passenger's buckle switch sensor 80 thatprovides a signal to controller 50 indicating whether the passenger hashis seat belt buckled. Passenger's weight sensors 82 located in thepassenger's seat 84 provide a signal indicative of the passenger'ssensed weight. Other passenger associated sensors 86 provide otheroccupant information to the controller 50 related to the passenger suchas position, height, girth, movement, etc. Other sensors 88 providesignals to the controller 50 indicative of whether a passenger ispresent on the seat 84, whether a child restraining seat is present onthe seat 84, etc.

In the preferred embodiment, the air bag restraining device 14 includesa first actuatable stage 90 and a second actuatable stage 92, e.g., twoseparate sources of inflation fluid in fluid communication with a singleair bag restraining device 14. Each stage 90, 92, has an associatedsquib (not shown) that, when energized with sufficient current for asufficient time period, initiates fluid flow from an associated fluidsource. When one stage is actuated, a percentage less than 100% of themaximum possible inflation occurs. To achieve a 100% inflation, thesecond stage must be actuated within a predetermined time of the firststage actuation. More specifically, the controller 50 performs a crashalgorithm using determined crash metrics and outputs one or more signalsto the actuatable restraining device 14 for effecting actuation of oneor both actuatable inflation stages 90 and 92 at times to achieve adesired inflation profile and pressure. As mentioned, other actuatablerestraining devices such as a pretensioner 22, or other devices such asside restraining devices 16 would be controlled in accordance with thepresent invention.

As mentioned, each of the actuatable stages 90, 92 includes anassociated squib (not shown) of the type well known in the art. Eachsquib is operatively connected to an associated source of gas generatingmaterial and/or a bottle of pressurized gas. The squibs are ignited bypassing a predetermined amount of electrical current through them for apredetermined time period. Each squib ignites its associated gasgenerating material and/or pierces its associated pressurized gasbottle. The amount of gas released into the bag is a direct function ofthe number of stages actuated and the timing of their actuation. Themore stages actuated during predetermined time periods, the more gaspresent in the air bag. In accordance with an embodiment, the air bagrestraining device 14 includes two actuatable stages. If only one stageis actuated, 40% of the maximum possible inflation pressure occurs. Ifthe two stages are actuated within 5 msec. of each other, 100% of themaximum possible inflation pressure occurs. If the stages are actuatedapproximately 20 msec. apart, a different, lesser percentage of themaximum possible inflation occurs.

By controlling the actuation timing of the multiple stages, the dynamicprofile of the bag is controlled, e.g., the inflation rate, theinflation pressure, etc.

The passenger's side restraining device 18 includes a first actuatablestage 94 and a second actuatable stage 96 controlled as described abovewith regard to the driver's side restraining device 14 to control thepercentage of maximum possible inflation pressure of the air bag.

In accordance with the present invention, a deployment controller 100within the controller 50 controls the actuation of the first actuatablestages 90, 94 and second actuatable stages 92, 96 using determined crashmetrics and other monitored sensor inputs.

The two substantially centrally located acceleration sensors 32, 36sense crash acceleration in the X direction. The first accelerationsensor 32 is used to determine crash metric values associated with anunbuckled vehicle occupant. The second acceleration sensor 36 is used todetermine crash metric values associated with a buckled vehicleoccupant.

Referring to FIGS. 3 and 4, a functional block diagram schematicallyrepresents certain of the control functions performed by the controller50 for the control of the driver's side, multistage restraining device14. It should be understood that the passenger's side, multistagerestraining device 18 is similarly controlled with differences notedbelow. Preferably, as mentioned, the controller 50 is preferably amicrocomputer programmed to perform these illustrated functions. Thedescription of “functions” performed by controller 50 may also bereferred to herein as “circuits.”

The acceleration sensor 32, preferably an accelerometer, outputs anacceleration signal CCU_1X having a characteristic (e.g., frequency andamplitude) indicative of the vehicle's crash acceleration upon theoccurrence of a crash event. The acceleration signal is filtered by,preferably, a hardware (i.e., separate from the controller 50)high-pass-filter (“HPF”)/low-pass-filter (“LPF”) 52 to eliminatefrequencies resulting from extraneous vehicle operating events and/orinput signals resulting from road noise. The frequency componentsremoved through filtering are not indicative of the occurrence of acrash event for which deployment of the restraining device 14 isdesired. Empirical testing is used to determine the frequency values ofrelevant crash signals for a particular vehicle platform of interest.Extraneous signal components that may be present in the crashacceleration signal are appropriately filtered and signalcharacteristics indicative of a deployment crash event are passed forfurther processing.

The accelerometer 32 preferably has a nominal sensitivity of ±100 g's (gbeing the value of acceleration due to earth's gravity, i.e., 32 feetper second squared or 9.8 m/s²). In a multistage actuatable restrainingsystem, it is desirable to continue sensing crash acceleration duringthe crash event, even after a first or initial trigger threshold isreached. Since a first stage actuation is desired upon the occurrence ofa crash acceleration well within ±100 g's, the further need for sensingis facilitated with the accelerometer 32 having a nominal sensitivity of±100 g's.

The filtered output signal 110 is provided to an analog-to-digital(converter) 112, which is preferably internal to the controller 50(e.g., an A/D input of a microcomputer) or an external A/D converter.The A/D converter 112 converts the filtered crash acceleration signal110 into a digital signal. The output of the A/D converter 114 isfiltered preferably with another high-pass/low-pass filter 116 havingfilter values empirically determined for the purpose of eliminatingsmall drifts and offsets associated with the A/D conversion. In amicrocomputer embodiment of the present invention, the filter 116 wouldbe digitally implemented within the microcomputer. A determinationfunction 118 of the controller 50 determines two crash metric valuesVel_Rel_1X (“crash velocity”) and Displ_Rel_1X (“crash displacement”)from this filtered crash acceleration signal. This is done by first andsecond integrations of the acceleration signal.

The crash displacement value and crash velocity value are preferablydetermined using a virtual crash sensing process fully described in U.S.Pat. No. 6,186,539 to Foo et al. and U.S. Pat. No. 6,036,225 to Foo etal. using a spring mass model of the occupant to account for springforces and damping forces. A detailed explanation of a spring-mass modelis found in U.S. Pat. No. 5,935,182 to Foo et al.

The values determined in function 118 are used to compare the Vel_Rel_1Xvalue as a function of Displ_Rel_1X against crash displacement varyingthresholds in a comparison function 124 and in a safing determinationfunction 128. The comparison function 124 compares the Vel_Rel_1X valueagainst a LOW threshold 130 or a SWITCHED LOW threshold 132 and alsocompares the Vel_Rel_1X value against a HIGH threshold 134. Thethresholds 130, 132, and 134 are selected for and associated with anunbelted occupant condition as sensed by the driver's buckle switch 70.It is desirable to, according to the present invention, deploy the firststage 90 when the Vel_Rel_1X exceeds the LOW threshold 130 or theSWITCHED LOW threshold 132 (depending on which is used by controller 50as described below) for the unbelted occupant condition. The secondstage 92 is actuated as a function of the time between a LOW (orSWITCHED LOW) threshold crossing and a HIGH threshold crossing which isdetermined by the crash severity index A function 140 for the unbeltedoccupant condition. All three thresholds 130, 132, and 134 vary as afunction of the crash displacement Displ_Rel_1X value and areempirically determined for a particular vehicle platform of interest.

A safing immunity box 142 is defined as a function of crash velocityVel_Rel_1X and crash displacement Displ_Rel_1X as shown in FIG. 4. Thesafing determination function 128 determines if the crash velocity valueVel_Rel_1X as a function of the crash displacement value Displ_Rel_2X isinside or outside the immunity box 142. If velocity value is outside ofthe immunity box, a HIGH or TRUE safing signal 144 is provided.Otherwise, the safing signal 144 is LOW or FALSE.

The occurrence of the crossing of the thresholds as determined infunction 124 are latched by latch 148. The crash severity indexing valueA for the unbelted occupant condition is determined in function 140 whena HIGH is received from an AND function 150. AND function 150 is ON orHIGH when two safing functions are satisfied, one based on the CCU_1Xsignal and the other based on the CCU_2X signal. The output of theSafing_A determination function 128 is one input of the AND function150. In general, the safing function 150 operates as a control mechanismfor enabling or disabling actuation of the first and second stages 90and 92 through the associated crash severity indexing functions 140 and190.

The crash severity indexing function A 140 is determined as a functionof the time period from when the determined crash velocity valueVel_Rel_1X exceeds the LOW threshold 130 or the SWITCHED LOW threshold132 to when it exceeds the HIGH threshold 134 and is referred to hereinas the “Δt measurement”. This value is a measure of the crash intensity.The shorter the time period, the more intense the vehicle crash. It isthis measure of Δt that is used in the control of the second stage 92for the unbelted occupant condition. The second stage is not necessarilydeployed at the time of the HIGH threshold crossing, but as a functionof the Δt measurement as fully described in the above-mentioned Foo etal. patents. Basically, the crash severity index function 140 caninclude a look-up table that is used to convert the Δt measurement intoa deployment time value that is used to control the timing of secondstage actuation.

The acceleration sensor 32 and the comparison function 124 are used forcrash discrimination when the vehicle occupant is in an unbeltedcondition. In an unbelted condition, the thresholds 130, 132, and 134are overall lower values than those that would be used if the vehicleoccupant was belted. The driver's buckle switch 70 is monitored by thecontroller 50 for use in consideration of the comparison function 124.Control of the passenger's restraining device 14 is similarly controlledtaking into consideration a belted or unbelted condition by monitoringthe condition of the passenger's buckle switch 80.

The acceleration sensor 36, preferably an accelerometer, outputs anacceleration signal CCU_2X having a characteristic (e.g., frequency andamplitude) indicative of the vehicle's crash acceleration parallel withthe X axis of the vehicle upon the occurrence of a crash event. Theacceleration signal is filtered by, preferably, a hardware (i.e.,separate from the controller 50) high-pass-filter(“HPF”)/low-pass-filter (“LPF”) 56 to eliminate frequencies resultingfrom extraneous vehicle operating events and/or input signals resultingfrom road noise. The frequency components removed through filtering arenot indicative of the occurrence of a crash event for which deploymentof the restraining device 14 is desired. Empirical testing is used todetermine the frequency values of relevant crash signals for theparticular vehicle platform of interest. Extraneous signal componentsthat may be present in the crash acceleration signal are appropriatelyfiltered and frequencies indicative of a deployment crash event arepassed for further processing.

The accelerometer 36 preferably has a nominal sensitivity of ±100 g's (gbeing the value of acceleration due to earth's gravity, i.e., 32 feetper second squared or 9.8 m/s²). In a multistage actuatable restrainingsystem, it is desirable to continue sensing crash acceleration duringthe crash event, even after a first or initial trigger value is reached.Since a first stage actuation is desired upon the occurrence of a crashacceleration well within ±100 g's, the further need for sensing isfacilitated with the accelerometer 36 having a nominal sensitivity of±100 g's.

The filtered output signal 160 is provided to an analog-to-digital (A/D)converter 162, which is preferably internal to the controller 50 (e.g.,an A/D input of a microcomputer) or an external A/D converter. The A/Dconverter 162 converts the filtered crash acceleration signal 160 into adigital signal. The output 164 of the A/D converter is filteredpreferably with another high-pass/low-pass filter 166 having filtervalues empirically determined for the purpose of eliminating smalldrifts and offsets associated with the A/D conversion. In amicrocomputer embodiment of the present invention, the filter 166 wouldbe digitally implemented within the microcomputer. The determinationfunction 168 of the controller 50 determines two crash metric valuesVel_Rel_2X (“crash velocity”) and Displ_Rel_2X (“crash displacement”)from this filtered crash acceleration signal CCU_2X in a similar manneras the determination made in function 118. This is done by first andsecond integrations of the filtered acceleration signal CCU_2X.

These crash displacement and crash velocity values are preferablydetermined using virtual crash sensing processing fully described inU.S. Pat. No. 6,186,539 to Foo et al. and U.S. Pat. No. 6,036,225 to Fooet al. using a spring mass model of the occupant to account for springforces and damping forces. A detailed explanation of a spring-mass modelis found in U.S. Pat. No. 5,935,182 to Foo et al.

The values determined by function 168 are used to compare the Vel_Rel_2Xvalue as a function Displ_Rel_2X against crash displacement varyingthresholds in a comparison function 174 and in a sating determinationfunction 178. The comparison function 174 compares the Vel_Rel_2X valueagainst a LOW threshold 180 or a SWITCHED LOW threshold 182 and comparesthe Vel_Rel_2X against a HIGH threshold 184. The thresholds 180, 182,and 184 are selected for and associated with a belted occupant conditionas monitored by the driver's buckle switch 70. It is desirable to,according to the present invention, deploy the first stage 90 when theVel_Rel_2X exceeds the LOW threshold 180 or the SWITCHED LOW threshold182 (depending on which is used) for the belted occupant condition. Thesecond stage is actuated as a function of the time from the LOW (orSWITCHED LOW) threshold crossing to the HIGH threshold crossing which isdetermined by the crash severity index B function 190 for the beltedoccupant condition. All three thresholds 180, 182, and 184 vary as afunction of the Displ_Rel_2X value and are empirically determined for abelted occupant condition. A safing immunity box 192 is defined as afunction of Vel_Rel_2X and Displ_Rel_2X as shown in FIG. 4. When theVel_Rel_2X value is outside of the immunity box 192, a HIGH or TRUEsafing signal 194 is provided to the second input of the AND function150. Otherwise, the safing signal 194 is LOW or FALSE. If both inputs tothe AND function 150 are HIGH, the output of the AND gate 150 is HIGHwhich will enable both crash severity indexing functions 140, 190.

The occurrence of the crossing of the thresholds as determined infunction 174 are latched by latch 198 and the crash severity indexingvalue B for the belted occupant condition is determined in function 190when a HIGH is received from the AND function 150.

The crash severity function B is determined as a function of the timeperiod from when the determined velocity value Vel_Rel_2X exceeds theLOW threshold 180 or the SWITCHED LOW threshold 182 to when it exceedsthe HIGH threshold 184 and is referred to herein as the “Δtmeasurement”. This value is a measurement of the crash intensity. Theshorter the time period, the more intense the vehicle crash. It is thismeasurement of Δt that is used in the control of the second stage forthe belted occupant condition. The threshold for the belted comparisonsused in function 174 are typically higher values than those for theunbelted condition used in comparison function 124. As similarlydescribed with reference to function 140, crash severity index Bfunction could include a look-up table to convert the Δt measurement toan actuation time for control of the second stage 92.

If the crush zone sensors 40, 42 detected certain events, the LOWthresholds 130, 180 are switched to the SWITCHED LOW thresholds 132, 182to control the deployment of the first stage 90 and for thedetermination of the Δt measurement used in the crash severity functions140, 190 that are, in turn, used to control the second stage 92.

The crush zone sensor 40 is preferably an accelerometer providing asignal CCU_3X having a characteristic (e.g., frequency and amplitude)indicative of the vehicle's crash acceleration upon the occurrence of acrash event as sensed at the forward, front left location of thevehicle. The acceleration signal CCU_3X is filtered by, preferably, ahardware high-pass-filter (“HPF”)/low-pass-filter (“LPF”) 58 toeliminate frequencies resulting from extraneous vehicle operating eventsand/or inputs resulting from road noise. The frequency componentsremoved through filtering are those frequencies not indicative of theoccurrence of a crash event. Empirical testing is used to establish afrequency range or ranges of the relevant crash signals so thatextraneous signal components present in the crash acceleration signalcan be filtered and frequencies indicative of a crash event passed forfurther processing. The accelerometer 40 preferably has a nominalsensitivity of ±250 g's.

The filtered output signal 210 is provided to an analog-to-digital(“A/D) converter 212, which may be internal to the controller 50 (e.g.,an A/D input of a microcomputer) or an external A/D converter. The A/Dconverter 212 converts the filtered crash acceleration signal 210 into adigital signal. The output of the A/D converter 212 is filteredpreferably with another high-pass/low-pass filter 214 having filtervalues empirically determined for the purpose of eliminating smalldrifts and offsets resulting from the conversion. In a microcomputerembodiment of the present invention, the filter 214 would be digitallyimplemented within the microcomputer. The filtering function 214 outputsa filtered acceleration signal 216.

The controller 50 determines an acceleration value designatedA_MA_CZS_3X. This value is determined by calculating a moving averagevalue of the filtered acceleration signal from the first crush zonesensor 40. A moving average is a sum of the last predetermined number ofsamples of the filtered acceleration signal. The average is updated byremoving the oldest value, replacing it with the latest sample, and thendetermining the new average. It has been determined that 4 to 32 samplesprovide a good average.

This determined crush zone sensor acceleration value A_MA_CZS_3X as afunction of the determined displacement value Displ_Rel_2X is comparedagainst an unbelted threshold 220 and a belted threshold 222 in athreshold comparison function 226. The belted threshold 222 and theunbelted threshold 220 vary as a function of Displ_Rel_2X in apredetermined manner to achieve the desired control. The thresholds maybe determined empirically for a particular vehicle platform of interest.If the A_MA_CZS_3X value exceeds the unbelted threshold 220, the lowerthreshold used in the comparison function 124 is switched to theSWITCHED LOW threshold 132. If the A_MA_CZS_3X value exceeds the beltedthreshold 222, the lower threshold used in the comparison function 174is switched to the SWITCHED LOW threshold 182.

The crush zone sensor 42 is preferably an accelerometer providing asignal CCU_4X having a characteristic (e.g., frequency and amplitude)indicative of the vehicle's crash acceleration upon the occurrence of acrash event as sensed at the forward, front right location of thevehicle. The acceleration signal CCU_4X is filtered by, preferably, ahardware high-pass-filter (“HPF”)/low pass filter (“LPF”) 60 toeliminate frequencies resulting from extraneous vehicle operating eventsand/or inputs resulting from road noise. The frequency componentsremoved through filtering are those frequencies not indicative of theoccurrence of a crash event. Empirical testing is used to establish afrequency range or ranges of the relevant crash signals so thatextraneous signal components present in the crash acceleration signalcan be filtered and frequencies indicative of a crash event passed forfurther processing. The accelerometer 42 preferably has a nominalsensitivity of ±250 g's.

The filtered output signal 230 is provided to an analog-to-digital(“A/D”) converter 232, which may be internal to the controller 50 (e.g.,an A/D input of a microcomputer) or an external A/D converter. The A/Dconverter 232 converts the filtered crash acceleration signal 230 into adigital signal. The output of the A/D converter 232 is filteredpreferably with another high-pass/low-pass filter 234 having filtervalues empirically determined for the purpose of eliminating smalldrifts and offsets resulting from the conversion. In a microcomputerembodiment of the present invention, the filter 234 would be digitallyimplemented within the microcomputer. The filtering function 234 outputsa filtered acceleration signal 236.

The controller 50 determines an acceleration value designatedA_MA_CZS_4X. This value is determined by calculating a moving averagevalue of the filtered acceleration signal of the crush zone sensor 42. Amoving average is a sum of the last predetermined number of samples ofthe filtered acceleration signal. The average is updated by removing theoldest value, replacing it with the latest sample, and then determiningthe new average. It has been determined that 4 to 32 samples provide agood average.

This determined crush zone sensor acceleration value A_MA_CZS_4X as afunction of the determined displacement value Displ_Rel_2X is comparedagainst an unbelted threshold 250 and a belted threshold 252 in athreshold comparison function 256. The belted threshold 252 and theunbelted threshold 250 vary as a function of Displ_Rel_2X in apredetermined manner to achieve the desired control. The values may bedetermined empirically for a particular vehicle platform of interest. Ifthe A_MA_CZS_4X value exceeds the unbelted threshold 250, the lowerthreshold used in the comparison function 124 is switched to theSWITCHED LOW threshold 132. If the A_MA_CZS_4X value exceeds the beltedthreshold 252, the lower threshold used in the comparison function 174is switched to the SWITCHED LOW threshold 182.

The central Y axis accelerometer 34 outputs an acceleration signalCCU_1Y to a filter 54. The filter signal from 54 is converted by an A/Dconverter 260 and digitally filtered by filter 262 in a similar manneras described above relative to processing of the signals fromaccelerometers 40, 42. From this filtered acceleration signal, a movingaverage acceleration value A_MA_CCU_1Y value (transverse crashacceleration) is determined using a moving average technique and avelocity value VEL_CCU_1Y value is determined by integration indetermining function 264. In comparison function 266, the determinedtransverse crash acceleration value A_MA_CCU_1Y as a function of thedetermined displacement value Displ_Rel_2X is compared against atransverse threshold 268. If the A_MA_CCU_1Y value exceeds thetransverse threshold 268, the LOW threshold used in the comparisonfunction 124 is switched to the SWITCHED LOW threshold 132 and the LOWthreshold used in the comparison function 174 is switched to theSWITCHED LOW threshold 182.

The A_MA_CCU_1Y value is also compared to an immunity box 276 defined bya predetermined A_MA_CCU_1Y value and a Displ_Rel_2X value as shown inFIG. 4 by a comparison function 278. If the A_MA_CCU_1Y value is outsideof the immunity box 276, a HIGH safing signal is provided for use with aside crash discrimination algorithm described below. Otherwise, thesafing signal is LOW.

The driver's side acceleration sensor 46 provides an acceleration signalRAS_1Y to a filter 62 which is converted by A/D converter 280. Thedigitized acceleration signal is further digitally filtered by filter282 and the filtered acceleration signal is provided to a driver sidediscrimination function 284.

The passenger's side acceleration sensor 48 provides an accelerationsignal RAS_2Y to a filter 64 which is converted by A/D converter 290.The digitized acceleration signal is further digitally filtered byfilter 292 and the filtered acceleration signal is provided to apassenger side discrimination function 294.

The driver side discrimination function and passenger sidediscrimination function can take any of several forms for sidediscrimination and control of the respective side restraining devices16, 20. In accordance with one embodiment, a driver's side accelerationvalue A_MA_RAS_1Y and a passenger's side acceleration value A_MA_RAS_2Yare determined using a moving average process in a similar manner asdescribed above with regard to other moving average accelerationdeterminations. These determined side acceleration values as a functionof the determined side velocity value VEL_CCU_1Y in both positive andnegative directions are compared against associated variable thresholds.If the values exceed their associated thresholds and the side safingsignal from function 278 is HIGH, the appropriate side restrainingdevice 16, 20 is actuated.

The crash severity INDEX_A 140 and the crash severity INDEX_B 190 areconnected to an adjustment function 300. The adjustment function 300receives further input signals from the driver's weight sensor 72 andfrom the other associated driver's sensors 76 mentioned above. Theadjustment function 300 adjusts the crash severity index values A or Bin response to the sensors 72, 76. Depending on the sensed weight of theoccupant and other sensed characteristics or attributes, the indexvalues A, B will be increased, decreased, or left without furtheradjustment.

The adjusted crash severity index values are passed to an inflatortranslator 310 which makes further adjustments to the crash severityvalues for the particular inflator or inflator type used in the vehicleplatform of interest. The translator can be used to select second stagedeployment times based on whether the LOW threshold was used or theSWITCHED LOW threshold was used for control of the first stage. Forexample, assume that a Δt time was 25 msec. If the SWITCHED LOWthreshold was used, the second stage could be actuated 25 msec. afterthe first stage actuation. However, if the “normal” LOW threshold (130,180) was used for control of the first stage with the same Δt, thesecond stage could be actuated 40 msec. after the first stage actuation.

The particular “inflator type” data can be input to the controller 50through appropriate sensors or can be prestored at the time of initialprogramming of the controller 50. In this way, the deployment of thefirst stage 90 and the second stage 92 could be advanced or retarded inresponse to the inflator type. For example, one vehicle may requireseries activation within 5 msec. to achieve 100% inflation. Anothervehicle may require series activation within 7 msec. to achieve 100%inflation because of a difference in inflator type.

The output of the translator 310, which is the adjusted Δt value, ispassed to the deployment controller 100. The deployment controller 100actuates the first actuatable stage 90 (subject to possible advancementor retarding by the adjustment function 300 and/or the translator 310)for the driver's multistage restraining device 14 when the threshold 130is exceeded and the driver buckle switch 70 indicates the driver isunbuckled and neither of the unbelted thresholds 220 or 250 were exceedby A_MA_CZS_3X and A_MA_CZS_4X, respectively, and A_MA_CCU_1Y did notexceed threshold 268.

The deployment controller 100 actuates the first actuatable stage 90(subject to possible advancement or retarding by the adjustment function300 and/or the translator 310) for the driver's multistage restrainingdevice 14 when the threshold 180 is exceeded and the driver buckleswitch 70 indicates the driver is buckled and neither of the beltedthresholds 222 or 252 were exceed by A_MA_CZS_3X and A_MA_CZS_4X,respectively, and A_MA_CCU_1Y did not exceed threshold 268.

The deployment controller 100 actuates the first actuatable stage 90(subject to possible advancement or retarding by the adjustment function300 and/or the translator 310) for the driver's multistage restrainingdevice 14 when the threshold 132 is exceeded and the driver buckleswitch 70 indicates the driver is unbuckled and one of unbeltedthresholds 220 or 250 were exceed by A_MA_CZS_3X and A_MA_CZS_4X,respectively, or A_MA_CCU_1Y exceed threshold 268.

The deployment controller 100 actuates the first actuatable stage 90(subject to possible advancement or retarding by the adjustment function300 and/or the translator 310) for the driver's multistage restrainingdevice 14 when the threshold 182 is exceeded and the driver buckleswitch 70 indicates the driver is buckled and one of the beltedthresholds 222 or 252 were exceed by A_MA_CZS_3X and A_MA_CZS_4X,respectively, or A_MA_CCU_1Y exceeded threshold 268.

If the restraining system includes a pretensioner 22, then thepretensioner is actuated when the first stage 90 is actuated if thebuckle switch indicates the driver is buckled.

The then determined Δt times are used to control when the second stage92 is actuated. The deployment controller 100 controls the actuation ofthe second stage 92 in response to the appropriate adjusted crashseverity index values Index_A or Index_B depending on the beltedcondition of the occupant. The controller 50 uses a look-up table havingpredetermined stored actuation times for control of the second stagedeployment in response to the appropriate crash severity index value.These stored values are determined through empirical methods for aparticular vehicle platform of interest.

Other sensors 88 could be used to make further control adjustments. Forexample, if a rearward facing child seat is detected on the passenger'sseat 84, actuation of the first and second stages 94, 96 could beprevented.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. For example, theswitched thresholds were responsive to both the crush zone sensorsCZS_3X and CZS_4X and in response to the side acceleration sensorCCU_1Y. The switching of the thresholds could have been responsive toonly the crush zone sensors CZS_3X and CZS_4X or only the transverseacceleration CCU_1Y. Such improvements, changes, and/or modificationswithin the skill of the art are intended to be covered by the appendedclaims.

Having described the invention, the following is claimed:
 1. Anapparatus for controlling a vehicle actuatable occupant restrainingsystem comprising: a first crash accelerometer sensing crashacceleration and providing a first crash acceleration signal indicativethereof; means for determining crash velocity in response to the firstcrash acceleration signal; means for determining crash displacement inresponse to the first crash acceleration signal; a controller actuatingthe actuatable occupant restraining system in response to the determinedcrash velocity as a function of crash displacement exceeding a selectedone of a discrimination threshold and a switched discriminationthreshold; a second accelerometer sensing transverse crash accelerationand providing a transverse crash acceleration signal indicative thereof;and said controller including means for comparing a value functionallyrelated to the transverse crash acceleration as a function of thedetermined crash displacement against a transverse threshold and meansfor selecting one of the discrimination threshold and the switcheddiscrimination threshold in response to the comparison of the valuefunctionally related to the transverse acceleration against thetransverse threshold.
 2. The apparatus of claim 1 wherein saidcontroller further includes means for comparing said determined crashvelocity against a high discrimination threshold and controlling asecond stage of said actuatable restraining system in response to thetime between said crash velocity exceeding the selected one of saiddiscrimination threshold and said switched discrimination threshold towhen said crash velocity exceeds said high discrimination threshold. 3.An apparatus for controlling a vehicle actuatable occupant restrainingsystem comprising: a first crash acceleration sensor sensing crashacceleration and providing a first crash acceleration signal indicativethereof; means for determining crash velocity in response to the firstcrash acceleration signal; means for determining crash displacement inresponse to the first crash acceleration signal; a controller actuatingthe actuatable occupant restraining system in response to the determinedcrash velocity as a function of crash displacement exceeding one of afirst discrimination threshold and a second discrimination threshold; asecond accelerometer sensing transverse crash acceleration and providinga transverse crash acceleration signal; and said controller includingmeans for comparing a value functionally related to the transverseacceleration as a function of the determined crash displacement againsta transverse threshold, said controller actuating said occupantrestraining system in response to said crash velocity exceeding saidfirst discrimination threshold and said value functionally related tothe transverse acceleration being less than said transverse thresholdand actuating said occupant restraining system in response to said crashvelocity exceeding said second discrimination threshold and said valuefunctionally related to the transverse acceleration is greater than saidtransverse threshold.
 4. An apparatus for controlling a vehiclemultistage actuatable occupant restraining system comprising: a firstcrash accelerometer sensing crash acceleration and providing a firstcrash acceleration signal indicative thereof; means for determiningcrash velocity in response to the first crash acceleration signal; meansfor determining crash displacement in response to the first crashacceleration signal; a controller for comparing the determined crashvelocity as a function of crash displacement against one of a lowdiscrimination threshold and a switched low discrimination threshold; asecond accelerometer sensing transverse crash acceleration; and saidcontroller including means for comparing a value functionally related tothe transverse crash acceleration as a function of the crashdisplacement against a transverse threshold, and means for selectingsaid one of said low discrimination threshold and said switched lowdiscrimination threshold in response to the transverse crashacceleration comparison, said controller actuating a first stage of saidmultistage occupant restraining system in response to said determinedcrash velocity exceeding the selected one of said low discriminationthreshold or switched low discrimination threshold.
 5. The apparatus ofclaim 4 wherein said controller further includes means for comparingsaid determined crash velocity against a high discrimination thresholdand controlling a second stage of said actuatable restraining system inresponse to the time between said crash velocity exceeding the selectedone of said discrimination threshold and said switched lowdiscrimination threshold to when said crash velocity exceeds said highdiscrimination threshold.
 6. A method for controlling a vehicleactuatable occupant restraining system comprising: sensing crashacceleration; determining crash velocity in response to the sensed crashacceleration; determining crash displacement in response to the sensedcrash acceleration; sensing transverse crash acceleration; comparing avalue functionally related to the transverse acceleration as a functionof the determined crash displacement against a transverse threshold;switching the value of the discrimination threshold to a switcheddiscrimination threshold when the value functionally related to thetransverse acceleration exceeds the transverse threshold; and actuatingthe actuatable occupant restraining system in response to the determinedcrash velocity as a function of crash displacement exceeding one of thediscrimination threshold and the switched discrimination threshold.
 7. Amethod for controlling a vehicle actuatable occupant restraining systemcomprising: sensing crash acceleration; determining crash velocity inresponse to the sensed crash acceleration; determining crashdisplacement in response to the sensed crash acceleration; sensingtransverse acceleration; and comparing a value functionally related tothe transverse acceleration as a function of the determined crashdisplacement against a transverse threshold; and actuating said occupantrestraining system in response to said crash velocity exceeding a firstdiscrimination threshold and said value functionally related to thetransverse acceleration being less than said transverse threshold andactuating said occupant restraining system in response to saiddetermined crash velocity exceeding a second discrimination thresholdwhen said value functionally related to the transverse acceleration isgreater than said transverse threshold.
 8. A method for controlling avehicle multistage actuatable occupant restraining system comprising thesteps of: sensing crash acceleration and providing a crash accelerationsignal indicative thereof; determining crash velocity in response to thecrash acceleration signal; determining crash displacement in response tothe crash acceleration signal; comparing the determined crash velocityas a function of crash displacement against one of a low discriminationthreshold and a switch low discrimination threshold; sensing transversecrash acceleration; comparing a value functionally related to transversecrash acceleration as a function of the crash displacement against atransverse threshold and selecting one of a low discrimination thresholdand a switched low discrimination threshold in response thereto; andactuating a first stage of said multistage occupant restraining systemin response to said determined crash velocity exceeding the selected oneof said low discrimination threshold and switched low discriminationthreshold.
 9. An apparatus for controlling a vehicle actuatable occupantrestraining system comprising: a crash accelerometer sensing crashacceleration and providing a crash acceleration signal indicativethereof; means for determining crash velocity in response to the crashacceleration signal; means for determining crash displacement inresponse to the crash acceleration signal; a controller actuating theactuatable occupant restraining system in response to the determinedcrash velocity as a function of crash displacement exceeding a selectedone of a low discrimination threshold and a switched low discriminationthreshold; a crush zone accelerometer for sensing crush zoneacceleration at a crush zone location of the vehicle and providing acrush zone acceleration signal indicative thereof; a transverseaccelerometer sensing transverse crash acceleration and providing atransverse crash acceleration signal indicative thereof; and saidcontroller including means for comparing a value functionally related tothe transverse crash acceleration signal as a function of the determinedcrash displacement against a transverse threshold, means for comparing avalue functionally related to the crush zone acceleration as a functionof the determined crash displacement against a crush zone threshold, andmeans for selecting one of the low discrimination threshold and theswitched low discrimination threshold in response to at least one of thevalue functionally related to the transverse acceleration exceeding thetransverse threshold and the value functionally related to the crushzone acceleration exceeding the crush zone threshold.
 10. A method forcontrolling a vehicle actuatable occupant restraining system comprising:sensing crash acceleration and providing a crash acceleration signalindicative thereof; determining crash velocity in response to the crashacceleration signal; determining crash displacement in response to thecrash acceleration signal; actuating the actuatable occupant restrainingsystem in response to the determined crash velocity as a function ofcrash displacement exceeding a selected one of a low discriminationthreshold and a switched low discrimination threshold; sensing crushzone acceleration at a crush zone location of the vehicle and providinga crush zone acceleration signal indicative thereof; sensing transversecrash acceleration and providing a transverse crash acceleration signalindicative thereof; comparing a value functionally related to thetransverse crash acceleration as a function of the determined crashdisplacement against a transverse threshold; comparing a valuefunctionally related to the crush zone acceleration as a function of thedetermined crash displacement against a crush zone threshold; andselecting one of the low discrimination threshold and the switched lowdiscrimination threshold in response to at least one of the valuefunctionally related to the transverse acceleration exceeding thetransverse threshold and the value functionally related to the crushzone acceleration exceeding the crush zone threshold.